Data over cable service interface specification (DOCSIS) is an international telecommunications standard that permits the addition of high-speed data transfer to an existing cable television system. Cable television operators use DOCSIS 3.0 to provide two-way communication over their existing hybrid fiber-coaxial (HFC) infrastructure.
An HFC network is a broadband network that combines optical fiber and coaxial cable. The HFC network is a two-way communication network between a cable modem termination system (CMTS) and a cable modem. The CMTS is communication equipment typically located in a cable operator's headend facility. The CMTS collects and processes communication signals, distributes those signals to customer locations using downstream channels, and receives other communication signals from the customer locations on upstream channels. The cable modem is a communication device that receives the communication signals on the downstream channels from the CMTS, and transmits the other communication signals to the CMTS on the upstream channels. The cable modem may be a standalone device that connects to the Internet, or integrated with the set-top box.
Channel bonding is a DOCSIS 3.0 feature that enables a cable modem at a customer location to use multiple downstream channels, or multiple upstream channels, together at the same time. For example, a cable modem configured with four upstream channels can use DOCSIS 3.0 channel bonding to increase the throughput of the upstream communication with the CMTS. The cable modem distributes, or segments, the data packets among the four channels in an upstream bonding group and transmits the data packets to the CMTS in parallel, rather than in series. When the upstream bonding group operates in full service mode, the CMTS receives and reassembles the data packets on all four channels in the upstream bonding group. If there is a problem receiving data packets on a CMTS receiver, due to an upstream channel that is associated with the receiver being impaired or unavailable, the CMTS cannot properly reassemble the data packets for the upstream bonding group and data loss or throughput degradation will result. The detection of this problem will allow communication to continue between the CMTS and cable modem by transitioning the upstream bonding group to operate in partial service mode by disabling data grant scheduling on the faulty receiver/channel. The prior art relies on the cable modem to detect the need to transition to partial service mode, and notify the CMTS. For example, the prior art DOCSIS method relies on the cable modem to detect power transmission issues due to ranging outside of the dynamic range power window for the cable modem. However, a cable modem cannot detect the impairment of an upstream channel. The cable modem can only infer the impairment because a channel can be impaired even though ranging messages can still make it through, and by the absence of the RNG-RSP messages from the CMTS after cable modem ranging intervals. Detection by the cable modem is a process that is unreliable and may result in significant time delay in the detection process. Thus, the prior art methods for transitioning from partial service mode to full service mode will allow the transition to occur before the channel is available, or perform the transition incorrectly, thereby resulting in data loss and performance degradation.
There is a need for a method of transitioning channels in an upstream bonding group from partial service mode to full service mode that minimizes data loss and maximizes performance. The presently disclosed invention satisfies this demand.